Plastic hot-water pipe systems and domestic water pipe systems are usually intended to be mounted inside a structure, such as a partition floor or a partition wall, by using protecting tubes. The pipe fittings are made to be of a colour different from the pipes, whereby they are clearly different from each other. Further, pipe fittings are typically provided with reinforcing ribs and other irregularities on the outer surface, which causes the fittings to gather dirt and makes it extremely difficult to keep the outer side of the pipe systems clean.
Solutions for connecting pipes to each other are disclosed in publications DE 19 735 919, DE 29 814 047 and DE 29 907 585, for example. The publications describe a solution comprising a pipe fitting made of metal or plastic, the end of which is arranged inside the pipe to be connected. A compression sleeve made of metal is typically arranged in the outside of the pipe to be connected, the sleeve being pressed around the pipe to guarantee the tightness of the connection between the pipe fitting and the pipe. Manufacturing costs of such pipe fittings are rather high, and in addition, modifiability of their appearance is rather difficult.
EP publication 0 530 387 also discloses a solution for providing a pipe connection, in which the end of the pipe to be connected is expanded, and it is pushed upon the pipe fitting. A compression band can further be arranged in the outside of the pipe to be connected, the band being made of plastic having a memory in such a way that the compression band arranged upon the connection tends to return to the smaller diameter remembered by the material, pressing the connection tight. The solution is rather functional and easy to use but requires the use of an expanding tool and therefore also the expanding of the pipe as a separate stage of operation in mounting.